Specs of the SK6812 LED strip

Posted on Thu 31 August 2023 in electronics

I was considering a SK6812 strip for a project of mine, but I found it very hard to find information online about the power consumption. So I ordered a test strip to do the measurements myself. The SK6812 is an individually addressable LED strip. I got the RGBW variant, where each dot has a Red, Green, Blue and White LED that can be controlled. The protocol used is similar to the WS2811/WS2812/WS2813 series, but reading 32 bits per LED instead of 24 bits. This is what I found.

  • The supply voltage is 5V
  • A 5m, 300 LED strip consumes about 70mA in idle condition, or 0.23mA/LED
  • My ESP32-based controller requires another 150mA, or a bit more when it's actively refreshing the LEDs
  • For the LED current, I measured the current for 1, 2, 5, 10, 20 and 40 LEDs, and determined the slope. The Red LED averages at about 7.98mA/LED at full brightness; Green is at 8.11mA/LED; Blue is 7.98mA/LED; White is 16.11mA/LED
  • 100% RGB gives 23.06mA/LED, 100% RGBW gives 38.9mA/LED

With these currents and only 5V to start from, voltage drop is a significant problem. Based on some measurements, I estimate the resistance between 2 LEDs to be around 6.2mΩ. The voltage drop increases approximately with the square of the number of LEDs, so this problem grows quickly!

I measured what minimum voltage is needed to avoid fading. To do that, I folded the strip to put the first & last LED next to each other and turned them on full brightness. Next, I pulsed the middle LEDs and watched for a brightness difference between the first LED (getting the full supply voltage) and last LED (getting the full voltage drop because of the middle LEDs). I increased the number of pulsing LEDs until I could see the last LED pulse as well. I was slightly surprised to find that I could drop down to 3.4V without noticing any dimming; I was expecting a higher threshold. When the voltage dropped to 3.37V (1 more pulsing LED in the middle), the fading was just noticeable.

So for my 5m 60LED/m strip, this means I need power injected for every 1.9m. Since you can power from either end, I can stretch this up to 3.8m before I need to inject power in the middle of a run. Note that these numbers assume you can inject 5V at that point. If the 5V power supply is not located right next to the strip, you should account for the voltage drop in the supply cables as well. To sidestep that problem, I'm thinking of using a 12V (or 24V) power supply, and put a 12V to 5V buck converter right next to the strip.

Color output

I measured the LEDs color with the Opple Light Master 3:

  • Red (x, y)=(0.6532, 0.2984)
  • Green (x, y)=(0.1637, 0.5288)
  • Blue (x, y)=(0.1609, 0.0709)
  • White (x, y)=(0.4181, 0.4259), CCT=3500K, ∆uv=0.019, so slightly greenish
  • 100% RGBW (x, y)=(0.3407, 0.3217), CCT=5100K, ∆uv=-0.014, so slightly purplish
  • 100%W + 55%R + 57%B corrects for the greenish tint and yields (x, y)=(0.4072, 0.3951), CCT=3500K, ∆uv=0.001